The main target for malware still is the PC. But in the past few years, Apple’s (NASDAQ:AAPL) Mac computers have seen more threats.

Perhaps the biggest security threat is for mobile devices — a market that’s growing at a torrid rate. (For example, devices using Google’s (NASDAQ:GOOG) Android operating system are seeing 1 million activations per day.) One pernicious virus on this front is “ransomware,” which will take control of a smartphone and only release it when a payment is made.

Consumers often do not realize the problems until it is too late. Naturally, this could be a big opportunity for security companies such as Symantec (NASDAQ:SYMC), which could find plenty of new growth from the mobile market.